1. Field of the Invention
The present invention broadly concerns a hydraulic work support having a plunger shiftable within a bore of a housing, wherein a fixed sleeve surrounding the plunger is radially deformable under the influence of hydraulic pressure to lock the plunger in any one of a number of extended positions. More particularly, the present invention is directed toward a work support assembly wherein all porting for the assembly is located at the end of the housing and hydraulic fluid is admitted along a path between the sleeve and the housing in a direction parallel to the central axis of the bore, in order to facilitate installation of the assembly in a wide variety of base structures and with a minimum number of components.
2. Description of the Prior Art
A variety of adjustable work supports are known to those in the art and are oten used in situations where it is advantageous to support a work piece at an intermediate location during the work operation. For the most part, these devices include a plunger which is longitudinally shiftable to move to a position of contact with the workpiece; also, a locking means is provided to thereafter hold the plunger in the adjusted position. In some cases, the plunger is movable under the influence of fluid pressure to engage the workpiece and a spring is provided for returning the plunger to a retracted position after the work operation is completed, while in other cases a spring of the assembly continuously biases the plunger toward an extended position and the latter is retracted by the weight of the workpiece to a desired, adjusted position for commencement of the work operation.
Certain of the known adjustable work support assemblies have an outer housing, a deformable, tubular sleeve received in a cylindrical bore of the housing, and a cylindrical plunger which is shiftable within the sleeve to a desired position for support of a workpiece. The sleeve and the bore of the housing are constructed to present an annular chamber surrounding the sleeve. Application of hydraulic fluid pressure to the chamber exerts a force directed radially inwardly on the deformable sleeve, which in turn contracts to grippingly engage the plunger and lock the same in a desired position. In this manner, a workpiece can be firmly supported at a number of spaced, intermediate locations as the work operation progresses.
One example of the aforementioned work support assemblies is described in U.S. Pat. No. 3,729,185, dated Apr. 24, 1973. In U.S. Pat. No. 3,729,185, hydraulic fluid is admitted to an annular space between a deformable sleeve and a housing along a passageway which extends laterally through a relatively thick wall of the housing and which terminates in a port extending radially away from the housing bore. Unfortunately, a number of seals must be provided for confining the pressurized fluid within the chamber, and the location of the passageway and the port effectively precludes the use of a relatively thin, space-saving housing which could optionally be deeply recessed within an opening of a work table. Furthermore, the hydraulic fluid piping connections are lcoated at the side of the work support assembly described in U.S. Pat. No. 3,729,185 which is unsatisfacotry in situations where sufficient clearance for the hydraulic piping is unavailable.
Other work support assemblies which have been constructed in the past are provided with a somewhat thinner cylindrical housing and a threaded cap which is received in one end of a bore of a housing. An externally threaded region on the housing enables installation of the assembly on a machine table or the like. Pressurized fluid for radial contraction of a sleeve enters a space between the sleeve and the housing through a small passageway which is located in the cap and which communicates with a groove in the sleeve that extends from the cap to the chamber. However, the cap is a component which must be machined to specific tolerances thereby representing a significant portion of the cost of the overall assembly, and in addition the overall length of the device must be increased by the height of the cap which in turn causes the depth of the bore within the work table to be correspondingly lengthened.